Electroacoustic transducer having a diaphragm made of at least one layer of piezoelectric material

ABSTRACT

An electroacoustic transducer comprising a thin-walled cylindrical sleeve with a vibrating diaphragm that includes at least one layer of piezoelectric material and rigidly secured at its peripheral edge to one end of the sleeve. This allows the diaphragm to perform a pivotal movement at its peripheral edge. In a second embodiment the sleeve is conical with the narrow end flanged inwardly and the diaphragm rigidly secured thereto. If the sleeve is metal, an integrated amplifier may be mounted thereon so that the sleeve acts as a heat sink.

O United States Patent 1 3,683,129

Roos et al. Aug. 8, 1972 [54] ELECTROACOUSTIC TRANSDUCER 3,104,336 9/1963 Harris ..179/110 F HAVING A DIAPHRAGM MADE OF AT 3,206,558 9/1965 Shoot ..179/1 10 A LEAST-ONE LAYER ()1? 2,448,352 8/1948 Carlin ..310/9.1 PIEZOELECTRIC MATERIAL 2,939,106 /1960 Mason ..179/110 3,222,462 12/1965 Karmann et al. ..310/9.] [72] Inventors: ,llaan Roos; lsalogloghlioone, 1022 3,305,638 2/1967 Teachout ..179/1 mmaslnge m oven, e erlands FOREIGN PATENTS OR APPLICATIONS [73] Assignee: U.S. Philips Corporation, New 878,087 9/1961 Great Britain ..340/

York, N.(. Primary Examiner-Kathleen H. Claft'y [22] Filed sept' 1969 Assistant ExaminerThomas L. Kundert [21] Appl. No.: 860,863 Attorney-Frank R. Trifari Foreign Application Priority Data [57] ABSTRACT An electroacoustic transducer comprising a thin- Sept. 30, 1968 Netherlands ..68l3993 walled cylindrical Sleeve with a vibrating diaphragm that includes at least one layer of piezoelectric materi- [22] "IN/1101;341:2410? a] and rigidly secured at its peripheral edge to one end d 0/9 1 9 4 of the sleeve. This allows the diaphragm to perform a 1 o earc 310/8 8 5 16 pivotal movement at its peripheral edge. in a second embodiment the sleeve is conical with the narrow end flanged inwardly and the diaphragm rigidly secured [56] References Cited thereto. 1f the sleeve is metal, an integrated amplifier UNITED STATES PATENTS gay bekmounted thereon so that the sleeve acts as a eat sin 2,967,956 1/1961 Dranetz et al. ..340/10 3,007,013 10/1961 Paull et a1 ..179/ A 7 Claims, 5 Drawing Figures 10101 III PATENTEDMI: 8 I872 III INVENTORS SALOMON BOONE AGEN T\ 1 ELECTROACOUSTIC TRANSDUCER HAVING A DIAPI-mAGM MADE OF AT LEAST ONE LAYER F PIEZOELECTRIC MATERIAL The present invention relates to a transducer for con- 'verting acoustic vibrations into electric oscillations,

and vice versa, in the form of a diaphragm with at least one layer of a piezo-electric material, the edge of the diaphragm being supported by a frame. Such transducers are particularly suitable for built-in use in a microphone.

It is known to use a transducer having a diaphragm which is divided into a plurality of elements. These elements are flexibly supported by a frame. In the embodiment of a microphone this frame is the microphone casing or a part thereof.

The invention is characterized in that the frame is a thin-walled sleeve, one end of which is rigidly secured to the edge of the diaphragm. This provides the advantage that the edge of the diaphragm is incapable of vibrating at right angles to its plane but his capable of pivotal movement.

An embodiment of the invention is characterized in that the edge of the diaphragm along its periphery is secured to the inner surface of the end of the sleeve. In this embodiment, the diaphragm is secured with a tight fit in the sleeve by means of an adhesive, for example, glue.

Another embodiment is characterized in that the sleeve is conical and in that at the end having the smaller transverse dimensions its edge is flanged inwardly, the diaphragm being secured along its periphery to the flange. In this case also, securing may be by means of glue.

For satisfactory pivotal movement of the diaphragm it has proved of advantage for the outer dimensions of the flanged edge to be slightly smaller than those of the diaphragm.

The sleeve may be made of a synthetic resin or of a metal. In the latter case its wall thickness will be smaller. When the sleeve is made of metal, for example, brass, it is particularly advantageous forthe amplifier associated with the transducer to be provided on the sleeve in the form of an integrated circuit. The sleeve then also serves as a heat sink for the energy dissipated in the integrated amplifier. The electrodes of the transducer then are directly connected to the contacts of the integrated amplifier. When the transducer is provided with an integrated amplifier on its frame, it may take the form of a built-in element for a microphone, and this facilitates, and saves time in, the assembly of the microphone.

The invention will now be described more fully with reference to the drawing, in which FIG. 1 is a cross-sectional view of a cylindrical diaphragm secured in a cylindrical sleeve,

FIG. 2 is a plan view thereof,

FIGS. 3 and 4 are a cross-sectional view and a plan view respectively of the frame in the shape of a conical sleeve according to the invention, and

FIG. 5 shows a detail of this conical sleeve provided with an integrated amplifier.

In the Figures, a transducer 1 of circular shape comprises two layers 2 and 3 of a piezo-electric material the outer surfaces of which are each provided with a metal electrode 4 and 5, respectively, provided by deposition from vapor. In FIGS. 1 and 2, the transducer 1 is cemented with a close fit in an end 8 of a cylindrical sleeve 6 the wall thickness of which is less than the thickness of the transducer 1. The other end 9 of the sleeve 6 is cemented to a fixed base 7. For use as a microphone, good results have been obtained with a transducer of diameter 15 mm and thickness about 300 pm and a tube wall thickness of about 40 pm.

For use as a microphone it has further proved of advantage for the transducer 1 of the form shown in FIG. 1 to be arranged, as shown in FIG. 3, on a conical thinwalled sleeve 10, which at its upper end 13, i.e., the end the transverse dimensions of which are smaller, has an inwardly flanged edge 12. On this flanged edge the transducer 1 is secured by means of cement. The other end 14 of the sleeve 10 is flanged outwardly, and the flanged edge 15 is secured to a fixed base 16.

Using a transducer of the specified kind, good results have been obtained with a sleeve having a wall thickness of about pm.

FIG. 5 shows an integrated amplifier 20 which, by means of a metal base plate 21, is secured to the inner surface of the conical sleeve 10. The integrated amplifier is provided with a number of contact areas which, by means of short connecting leads, are connected to contacts 22 to 25 arranged in the conical sleeve 10 around the integrated amplifier. The electrode 4 is connected to the contact 22, for example, by means of a conductor deposited from vapor. The electrode 5 is connected to one of the remaining contacts through the metal sleeve 10.

What is claimed is:

1. An electroacoustic transducer comprising a thinwalled housing sleeve, a vibrating diaphragm including at least one layer of piezoelectric material, the wall thickness of the sleeve being less than the thickness of the diaphragm, and means for rigidly securing the outer peripheral edge of the diaphragm directly to the inner surface of one end of said thin-walled sleeve so that the peripheral edge of the diaphragm performs a pivotal movement.

2. An electroacoustic transducer comprising a thinwalled housing sleeve, the sleeve comprising a conical member with the smaller diameter end having its edge flanged inwardly a vibrating diaphragm including at least one layer of a piezoelectric material, means for rigidly securing the peripheral edge of the diaphragm to the flange so that the peripheral edge of the diaphragm performs a pivotal movement.

3. A transducer as claimed in claim 2, characterized in that the outer dimensions of the sleeve at the area of engagement of the flange with the diaphragm are slightly smaller than the outer dimension of the diaphragm.

4. A transducer as claimed in claim 2 wherein the wall thickness of the flange in the axial direction is less than the thickness of the diaphragm in said axial direction.

5. An electroacoustic transducer comprising a thinwalled housing sleeve made of metal, a vibrating diaphragm including at least one layer of a piezoelectric material, means for rigidly securing the peripheral edge of the diaphragm to one end of said thin-walled sleeve so that the peripheral edge of the diaphragm performs a pivotal movement, and an amplifier for the:

transducer signals mounted on the sleeve in the form of an integrated circuit.

smaller end whereby the peripheral edge of the diaphragm performs a pivotal movement.

7. A transducer as claimed in claim 6 wherein the peripheral edge of the diaphragm is rigidly secured to the flange by engagement of one surface only of the diaphragm. 

1. An electroacoustic transducer comprising a thin-walled housing sleeve, a vibrating diaphragm including at least one layer of piezoelectric material, the wall thickness of the sleeve being less than the thickness of the diaphragm, and means for rigidly securing the outer peripheral edge of the diaphragm directly to the inner surface of one end of said thin-walled sleeve so that the peripheral edge of the diaphragm performs a pivotal movement.
 2. An electroacoustic transducer comprising a thin-walled housing sleeve, the sleeve comprising a conical member with the smaller diameter end having its edge flanged inwardly a vibrating diaphragm including at least one layer of a piezoelectric material, means for rigidly securing the peripheral edge of the diaphragm to the flange so that the peripheral edge of the diaphragm performs a pivotal movement.
 3. A transducer as claimed in claim 2, characterized in that the outer dimensions of the sleeve at the area of engagement of the flange with the diaphragm are slightly smaller than the outer dimension of the diaphragm.
 4. A transducer as claimed in claim 2 wherein the wall thickness of the flange in the axial direction is less than the thickness of the diaphragm in said axial direction.
 5. An electroacoustic transducer comprising a thin-walled housing sleeve made of metal, a vibrating diaphragm including at least one layer of a piezoelectric material, means for rigidly securing the peripheral edge of the diaphragm to one end of said thin-walled sleeve so that the peripheral edge of the diaphragm performs a pivotal movement, and an amplifier for the transducer signals mounted on the sleeve in the form of an integrated circuit.
 6. An electroacoustic transducer comprising a thin-walled housing sleeve, the sleeve comprising a conical member with the smaller diameter end flanged inwardly from the inner surface of the sleeve, a vibrating diaphragm including at least one layer of a piezoelectric material, means for rigidly securing the peripheral edge of the diaphragm to the flange so as to extend radially beyond the outer surface of the sleeve at said smaller end whereby the peripheral edge of the diaphragm performs a pivotal movement.
 7. A transducer as claimed in claim 6 wherein the peripheral edge of the diaphragm is rigidly secured to the flange by engagement of one surface only of the diaphragm. 